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References: <20240326-zswap-xarray-v9-1-d2891a65dfc7@kernel.org> <CANeU7Q=8p4whMu+H9GXqQc4Ehjt0_kCtNdg34TiW4bWFw03dbw@mail.gmail.com>
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From: Nhat Pham <nphamcs@gmail.com>
Date: Tue, 26 Mar 2024 14:04:01 -0700
Message-ID: <CAKEwX=MLFaA-1kYbKT0bMuTsJDqK9ZfoJ+WUyxM4tBu_owyPYA@mail.gmail.com>
Subject: Re: [PATCH v9] zswap: replace RB tree with xarray
To: Chris Li <chrisl@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org, 
	linux-mm@kvack.org, Yosry Ahmed <yosryahmed@google.com>, 
	Johannes Weiner <hannes@cmpxchg.org>, "Matthew Wilcox (Oracle)" <willy@infradead.org>, 
	Chengming Zhou <zhouchengming@bytedance.com>, Barry Song <v-songbaohua@oppo.com>
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On Tue, Mar 26, 2024 at 11:42=E2=80=AFAM Chris Li <chrisl@kernel.org> wrote=
:
>
> > -        * When reading into the swapcache, invalidate our entry. The
> > +        * When reading into the swapcache, erase our entry. The
> >          * swapcache can be the authoritative owner of the page and
> >          * its mappings, and the pressure that results from having two
> >          * in-memory copies outweighs any benefits of caching the
> > @@ -1649,8 +1581,12 @@ bool zswap_load(struct folio *folio)
> >          * the fault fails. We remain the primary owner of the entry.)
> >          */
> >         if (swapcache)
> > -               zswap_rb_erase(&tree->rbroot, entry);
> > -       spin_unlock(&tree->lock);
> > +               entry =3D xa_erase(tree, offset);
> > +       else
> > +               entry =3D xa_load(tree, offset);
>
> This is the place I make the modification for the conflict resolution.
> It depends on the swapcache to execute xa_erase() or xa_load().
> Obviously, the xa_load() will not delete the entry from the tree.
>

The conflict resolution itself LGTM. I'll let you and Johannes decide
on the comment (but FWIW, the original meaning still holds, so I don't
see why we need to fix it).

Reviewed-by: Nhat Pham <nphamcs@gmail.com>